An active device of an AMLCD (Active Matrix Liquid Crystal Display), and a switching device and a peripheral circuit of an electro-luminescence device mostly use a polycrystalline silicon thin-film device.
A conventional method for converting an amorphous silicon film to a poly-crystalline silicon film uses high-temperature heat treatment and a laser.
The method for re-crystallizing the amorphous silicon film by means of laser beam radiation can perform a low-temperature process at 400° C. or less and manufacture a polycrystalline silicon thin-film in which field-effect mobility is high. However, it is difficult for the laser-based method to ensure uniformity of a crystallized sample when fabricating a large-area sample. There is a problem in that the laser-based method requires high-priced laser equipment, such that alternative technology is required.
The method using high-temperature heat treatment fabricates the polycrystalline silicon thin-film by means of a heat treatment process at a high temperature of 600° C. or more for a relatively long time. The method using high-temperature heat treatment necessarily requires a high crystallization temperature and a long heat treatment time. Because grains crystallized by the above-described method have many flaws, there is a difficulty in fabricating a device. Moreover, the method using high-temperature heat treatment has a problem in that a glass substrate cannot be used at a high crystallization temperature.
A crystallization method using metal has been recently proposed. The re-crystallization method using metal is a metal induced crystallization method and a metal induced lateral crystallization method. The crystallization method using metal can form a uniform thin-film in which a polycrystalline silicon thin-film transistor has high field-effect mobility. There is a problem in that a polycrystalline silicon thin-film fabricated by the re-crystallization method using metal has a limitation of electric characteristics due to a structure flaw within a thin film at a device manufacturing time. To address this problem, the re-crystallization method using metal requires a high-temperature heat treatment process at 800° C. or more or a re-crystallization process using a laser.
However, there is a problem in that the conventional method using a glass substrate cannot be used in a process at 600° C. or more and hence cannot perform a re-crystallization process at a high temperature.